Nuclease activity is ubiquitous in nature and is normally present in any fermentation broth. Some nucleases are known to be very stable.
Sometimes it is very important that the subtilisin product obtained from a fermentation broth is without nuclease activity; e.g., if the subtilisin product is to be used for removal of nucleases when isolating DNA and RNA from tissues or cell lines or if the subtilisin product is to be used for isolating PCR or RT-PCR templates.
It is known from “Biotechnology Techniques, Vol. 6, No. 1, 1992, p. 53-54” that a thermostable alpha-amylase when heated to 80° C. for 20 minutes may retain>90% of its activity and at the same time lose all DNAase activity.
Subtilisins are normally not able to tolerate such a long heat treatment at 80° C. and will lose a significant part of its activity.
Our inventors have found an improved method of inactivating the nuclease activity and keeping most of the subtilisin activity.